The selection of a suitable crystal will normally be performed under oil using an optical microscope. This method is adapted by using different oils and grease if the sample is not completely stable.
A vacuum line is available for obtaining crystals from Schlenks and other such vessels whilst keeping the remaining sample under an inert atmosphere. There is access to a glove box if sample too sensitive to use the vacuum line.
For thermally sensitive samples a 'crystal cooler' device allows a flow of cold nitrogen over the crystals whilst under the microscope.